Construction of dams submerges large areas of forests,how does this contribute to the greenhouse effect?

State whether the following statement is true or false:
Solar cells are made of semiconductor materials.

Ram visited Manikaran Sahib in Himachal Pradesh where he saw an experimental geothermal plant. When he saw a hot spring,he wanted to know more about it. His father explained to him about geothermal energy and hot springs. Now answer the following questions:
$(a)$ What did Ram's father explain to him about hot springs?
$(b)$ Why is geothermal energy not generated on a large scale?
$(c)$ What is the main advantage of using geothermal energy?

What is the effect of light on the conductivity of a semiconductor used in solar cells?

The fuel used in thermal power plants is:

Mention three advantages of converting domestic sewage to sewage gas.